11. In the 1960's, scientists discovered the mechanism that was responsible for plate movement, which is?

plate tectonics

Explanation:

The idea that the seafloor itself moves and also carries the continents with it as it spreads from a central rift axis was proposed by Harold Hammond Hess from Princeton University and Robert Dietz of the U.S. Naval Electronics Laboratory in San Diego in the 1960s. The phenomenon is known today as plate tectonics.